PROJECT SUMMARY/ABSTRACT Stroke injury is a process that occurs over a long duration with pathologic changes that result in long-term neurologic dysfunction. For stroke, there exists an important need for a strategy that can provide safe and efficacious stabilization to the hypoperfused brain and initialize long-lasting endogenous neuroprotection for prevention of long-term neurologic dysfunction. Sufficient evidence has shown that xenon (Xe), a bioactive gas, has profound neuroprotective effects with advantages of rapid diffusion across the blood-brain barrier (BBB) with minimal side effects. In recent novel studies, researchers at The University of Texas Health Science Center at Houston (UTHealth) incorporated Xe into liposomes and demonstrated that Xe-liposome treatment post-stroke resulted in activation of endogenous brain protection following ischemic stroke and subarachnoid hemorrhage. Corroborated mechanisms of Xe cytoprotection include the activation of endogenous cytoprotective molecules. Repetitive administration of Xe-liposomes extends the protective effects over time. Although the detailed mechanisms underlying repetitive administration induced long-term protection remain unclear, emerging evidence supports that such adaptive phenotypes are epigenetically mediated. As epigenetic post-conditioning is highly related to the potency, frequency and duration of stimuli, we hypothesize that repetitive intermittent Xe- liposomal administration at an optimal frequency and duration can induce epigenetic post-conditioning resulting in long-term effects. This hypothesis leads to the collaboration between Zymo Research Corporation (Zymo), an experienced epigenetics company, and UTHealth. UTHealth holds the patents containing the claims for the use of Xe-containing liposomes for prevention and treatment of stroke. From a commercialization standpoint, Xe- liposome is an attractive therapeutic candidate due to its low side effects and markedly high BBB diffusion. The goals of this proposal are to optimize the Xe-liposomal administration protocol for long-term cytoprotection, and to find the best epigenetic markers that directly correlate Xe treatment to long-term cytoprotective effects in stroke treatment. Our aims are: 1) to determine the optimal frequency and duration of Xe-liposomal administration and demonstrate sustained cytoprotection by repetitive Xe-liposomal administrations for ischemic stroke treatment; and 2) to determine epigenetic signatures to indicate Xe-sustained cytoprotection. Our long-term goals (STTR Phase II and beyond) are to develop an optimal Xe-liposomal delivery strategy using essential epigenetic markers to demonstrate acute and long-term neuroprotection following stroke, and to translate this technology into a clinical product with sustained stroke stabilization effects.